Stencil



.3 causes rusting and corrosion of typewriter steiicihzable;

Patented Mar. 21,. 1933- I p UNITED [STATES PATENT OFFICE I CARL rnmnmcn nRAUER, or srnrrm, 'elmmnr I m Drawing. Application filed April 16; 1931, Serial No; 530,723, and in Germany October 28, 1830.

his invention relates to stencil sheets I It is among the objects of this invention adapted for the reproduction of written and to provide stencil sheets having a coatlng typewritten matter. which is type-impressible without moisten- Stencil sheets have been made generally mg or otherwise treating it before being 5 from a base sheet of open texture, fibrous cut, 1s strong, free from pinholes, and not paper provided with a coating that is imsubject toc'racking produces clean and sharp pervious to ink, but which may be cut on copies, may be made from a composition atypewriter or with a stylus to permit the that is simple and readily prepared and used, passage of ink for reproduction of copies. and which overcomes or minimizes the dis;

The paper base commonly used is that known advantages of prior stencil sheets. 5 i

in the art asYo'shino; Although various The invention is predicated upon my diskinds of coating materials have been used, covery that satisfactory stencil sheets emall of the-stencils heretofore commercially bodying the objects stated may be prepared available have been subject to certain disfrom gelatin without hardening or coa advantages. lating it. In accordance with the invention 6 The firs stencils had a coating ofwax. this is accomplished by coating or impreg- Such coatings are readily cracked and bro- Hating an open texture, fibrous base, such, as

ken, which permits the ink to penetrate the Yoshino, wlth a composition adapted to stencil and spoil the copies, and they are form a coating of non-coagulated gelatin affected adversely by varying climatic conhaving homogeneously dispersed therev ditions. 'The wax stencils were largely suthrough an oily soft p pgag, .I and a stabiperseded by those having a coating of gelatin l1z1ng material, .As used herein th te -E coagulated, or hardened, by achromium stablllzer' and stabilizing material have salt, formaldehyde, or the like agent. These reference tosubsta'nces which do not coagutanned gelatin stencils are very strong and late the gclatln but maintain the coating have a long useful life, but they must be supple and homogeneous, and prevent sweatmoistened .to render the coating type-iming out of its ingredients. The coating thus pressible. This is disadvantageous because provided can be cut with type or stylus with the liquid used for moistening the stencils out moistenin and is therefore directly so parts. 'Also, the sheets stretch when mois- In the practice of this invention the coat tened, and" therefore the material to be relng composition is made by swelling, or disroduced may become distorted either durtending, a gelatin having suitable strength. "ing cutting of the wet'stencil, or during its 'lVater may be used for this purpose, but it 3 drying. The coagulated gelation stencils is preferred to amplify the swelling due to ffurthermore have had considerable tendency Water by means of an acid. Agetig acid is to formpin holes in the coating which perpreferred for this purpose because it effects mit ink to seep through and spot the copies an even and uniform swelling and distribu made from them. tion of the gelatin in the coatingicomposi- More recently there have been developed tion. The acid appears also to dissolve the the so-called dry stencils, whose coating comgelatin somewhat, and this is helpful in obprises a cellulose compound, such as cellu-' taining a homogeneously dispersed composi lose nitrate, softened and rendered type imtion. To the gelatin solution there is added gres'sible by oils. Such cellulose dry stencils a softening agent in an amount sufficient t 0 not require moistening, and they are satrender the gelatin in the coating soft and isfactorily strong at first. But the oils tend type-impressible. Oleic acid may be, and to sweat out, and this impairs the keeping preferably is, used for this purpose. The qualities of the stencils and causes damage composition preferably includes also a'fixed to the rubber parts of the typewriter which solvent, such as Turkey red' oil, which also 50 come in contact with them. has oily characteristics. The Turkey red 9 i of the oleic acid.

oil preferably is usedwith anothersolvent,

such as alcoho v Stencil sheets preparedfrom a composition containing the materials just described 5 are stencilizable to give satisfactory results. However, they have a tendency to exude a certain amount of the oil incorporated in the .coating'solution, and they harden and become brittle. This reduces the impressibility of the coating and leakage of ink through the cracks soils the copy paper.

The invention is predicated in part upon my discovery that these disadvantages may be overcome and fully satisfactorystenci v sheets produced by incorporating with the coating composition a material adapted to maintain the ingredients in the coating in a homogeneous stable co dition. Such materials are herein termed stabilizers. I have discovered that the higher chlorinated na hthalenes are particularly suitable for this purpose, an especially the hexachlorinate d naphthalenes. I now believe the beneficial action to be due to formation of a solid 26. solution with the oleic acid. Be that as it may, the stabilizers maintain the coatings homogeneous and stencilizable, and they minimize the disadvantages of unhardened gelatin coatings not containing them.

dis ersed readily al'co ol or Turkey red oil. Other stabilizers may be used instead of the chlorinated napthalenes referred to; e g., either palmitic pr stearic acids, both of which are stabilizers, may be used, in which case the palmitic or stearic acid replaces a portion Compositions containing these stablili'zers have excellent coating 40 qualities, and they provide stencil sheets having a coating that does not exude its ingredients, does not become brittle, and remains homogeneous. The sheets produce clear and clean copies,-and, because the stabilizers do not irreversibly harden, or coagulate" the gelatine, they are ready for immediate use,-

i. e. they are stencilizable.

the composidirectly There may be added also to tion a small amount of a cellulose ester, such as cellulose nitrate, This also tends 'to'maintain the homogeneity of the copting .the sheet. For this purpose the cellulose ester may be incorporate in the oleic acid, or dissolved in a solvent such as butyl acetate. In this connection it is to be observed that the cellulose ester represents a preferred addition, and when so used constitutes a minor roportion onlyof the coating.

In the preferred practice of the invention one part of powdered ten parts of water. After the gelatin has begun to swell there is added acetic acid equivalent to 6 per cent of glacial acid calculated upon the dry weight of the gelatin.

lby

' in butyl acetate. The mixture of oleic acid,

These chlorinated 'naphtllalenes can be in a solution conta nlng The mixture is alrcwed to stand at room, or slightly above room, temperature until it has become thick and highly viscous and will remain so at room temperature.

There is prepared also a second solution comprising about one and one-half parts of hexachlornaphthalene and two parts of oleic both calculated upon the dry gelatin weight. These ingredients are dissolved in double the quantity of a solution of equal parts of alcohol and Turkey red oil. This second solution is quite clear and transparent.. The coating composition is then made mixing two arts of the latter solution the thick gelatin solution, the mixture bein vigorously agitated or stirred until a per ectly homogenous dispersion has been obtained.

In case it is desired to use the cellulose ester referred to hereinabove, there may be 85 added to the solution of hexachlornaphthalene and oleic acid about 0.5 per cent (calthe total. of the final mixture) of cellulose nltrate in the form of a solution with one part 0 y and cellulose nitrate is then added to the gelatin solution in the proportions just described. F

Stencil sheets are made by drawing Yoshino paper through or over the composition, the excess composition being re-' moved, and the sheets dried. This procedure is well known in the art and requires no further detailed description. During coating of the sheets it is advisable to warm the'coa'ting composition somewhat so as to reduce its consistency and prevent it from getting too thick. When the sheets are drawnthe coating mass is milky in appearance, dried it becomes transparent, uniform and readily stencilizable. It will be understood that colored coatings may be provided by dissolving a dye in the composition, orsuspending a coloredpigment init.

According to the provisions of the patent statutes, I have explained the principle of my invention, and have 'described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim as my invention: 1. A directly stencilizable stencil sheet comprising an open texture 'fibrous base coated with a composition including gelatin highly distended in an aqueous solution of acetic acid and having homogeneously dissub - comprising an maintaining the homogeneity and permanence of the coating.

2. directly stencilizable stencil sheet homogeneously dispersed therethrough oleic acid and chlolorinated naphgelatin having homogeneously dispersed therethrough a solid solution acid supple, and said stabilizermaintalnlng the omogeneity and permanence of the coating. 4. directly stencilizable l1zer of the group comprism chlorinated naphthalene,-palm1tic ac1d an stearic acid, said stabilizer being present in an amount less than the oleic acid, and a mlno'r proportion of a cellulose ester, the homogeneity and permanence of the coating being maintained by said stabilizer and ester.

directly stencilizable stencil comprising an open texture fibrous aving' a coating of gelatin in anunhardened and uncoagulated highly distended condition, the gelatin having homogeneously dispersed therethrough oleic acid, a noncoagulating stabilizer of th an amount less ac1d, a minorproportlon of'a manence of the coating.

and Turkey red oil, the homogeneity and permanence of the coating being maintained by said stabilizer and ester; process of making a directly stencilizable stencil sheet, comprisingcoating an open texture fibrous base with a coatin composition of gelatin, oleic acid, and a non-coagulating stabilizer of the group comprising chlorinated naphthalene, palmitic acid acetic sorptive of said oleic gelatin in the coated and permanence of the coating.

8. A process of making a directly stencilizable stencil sheet comprising coating an proportion of cellulose ester, said acetic acid rendering the gelatin highly absorptive of the remaining ingredients, the gelatin the coated sheet being in an unhardened and uncoagulated condition, andthe homogeneity and permanence of the coating being maintained by said stabilizer and cellulose ester.

the gelatin havin ly dispersed therethrough urkey red oil and a solid solution of a major proportion of oleic acid and a minor roportion of a non-coagulating stabilizer ofthe group comprising chlorinated naphthalene, palmitic acid, and stearic acid, said oleic acid rendering the coating supple, andsaid stabilizer maintaining the homogeneity and permaking a directly stencilizable stencil sheet comprising coating-an open texture fibrous base with a coating composition of gelatin, aqueous acetic acid,

homogeneousac1d rendering the gelatin highly aburkey red oil, oleic acid, a stabilizer'in an amount less than said oleic acid and selected from the group comprising chlorinated naphthalene, palmitic acid and stearic acid, cellulose ester, said acetic acid rendering the gelatin highly absorptive of the remaining ingredients, the

elatin in the coated sheet b ardened and uncoagulated condition and the homogeneity and permanence o the coating belng maintained by said stabilizer and cellulose ester.

In testimony whereof, I hereunto sign my name.

CARL FRIEDRICH BRAUER' eing 1n an un- 

